alan_m wrote:

Is there a downside to using this polishing paste?

Can't see one, although it certainly does contain polishing ingredients,
it felt more like cleaning than polishing to use it, so their claim that
it is matched to enamel's hardness seems true, they do another version
for acrylic baths

Could it make the
surface too slippery to be safe when stepping in or out of the bath?

Not a problem with this bath, it has sand sprinkled within the enamel
for grip.